This invention relates to a process for preparing 3-acylamido or 3-diacylamido-4-haloazetidin-2-ones represented by the following general formula ##STR3## wherein X is chloro, bromo or iodo; R.sub.1 is an acylamido or diacylamido group having either the natural .beta.-configuration or the epi(.alpha.-) configuration; and R is a carboxy-protecting group.
The 4-haloazetidinones provided by the process of this invention are useful intermediates in the preparation of .beta.-lactam antibiotics. For example, S. Wolfe, U.S. Pat. Nos. 3,948,927, 3,950,352, 4,013,653, and 4,071,512, teaches the use of 4-haloazetidinones in the preparation of the so-called 1-oxapenicillins and the corresponding 1-oxa(dethia)cephalosporins. S. Wolfe, Canadian Journal of Chemistry, 52, 3996-3999 (1974) teaches the same use for the 4-haloazetidinones. Further, Narisada, Heterocycles, Vol. 7, No. 2 (1977) pp. 839-849 reports the preparation of 1-oxa-.beta.-lactam antibiotics with 4-haloazetidinones.
The usefulness and general versatility of the 4-haloazetidinones as intermediates for .beta.-lactam antibiotics has prompted research directed to alternative methods for their preparation from readily available and economic starting material.